1. Field of the Invention
The present invention relates to a method and a device to localize reclinear contours in a digitized image.
The invention shall be described chiefly in the context of an application to the analysis of a scene in which it is sought to recognize shapes characterized by rectilinear contours.
It is thus, for example, that when it is sought to localize man-made objects (roads, bridges, railways, canals etc.) in a natural environment, in infrared images produced by a camera placed on board an aircraft, such objects when observed generally appear in a polygonal shape. As a typical application, we might cite path-correction operations in aircraft navigation.
This application to shape recognition does not, however, restrict the scope of the present invention, which can also be used for other applications necessitating the extraction of dots of rectilinear contours, for example stereovision applications.
In general, image processing is done in three steps, namely:
the search for the dots that may belong to rectilinear contours;
the analytical description of the segments formed by these dots, and
the grouping of the various segments, thus detected and analyzed, that belong to one and the same object being searched for.
The invention relates to the first one of these steps, namely the preliminary search, in the unprocessed image, for rectilinear contours and the distinguishing of these contours from the other dots of the image. The results produced by the method and device of the invention will then be used as the basis for the downline processing corresponding to the next two steps.
2. Description of the Prior Art
Up till now, the processing algorithms and the types of physical architecture used have not provided for a localization, such as this, of the rectilinear contours in real time (namely at the video rate of the images produced) and have been even less capable of providing for the full processing of the image, as constituted by the three steps mentioned here above.